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71.
72.
Brian Miller Richard Reading Courtney Conway Jerome A. Jackson Michael Hutchins Noel Snyder Steve Forrest Jack Frazier Scott Derrickson 《Environmental management》1994,18(5):637-645
This paper discusses common organizational problems that cause inadequate planning and implementation processes of endangered
species recovery across biologically dissimilar species. If these problems occur, even proven biological conservation techniques
are jeopardized. We propose a solution that requires accountability in all phases of the restoration process and is based
on cooperative input among government agencies, nongovernmental conservation organizations, and the academic community. The
first step is formation of a task-oriented recovery team that integrates the best expertise into the planning process. This
interdisciplinary team should be composed of people whose skills directly address issues critical for recovery. Once goals
and procedures are established, the responsible agency (for example, in the United States, the US Fish and Wildlife Service)
could divest some or all of its obligation for implementing the plan, yet still maintain oversight by holding implementing
entities contractually accountable. Regular, periodic outside review and public documentation of the recovery team, lead agency,
and the accomplishments of implementing bodies would permit evaluation necessary to improve performance. Increased cooperation
among agency and nongovernmental organizations provided by this model promises a more efficient use of limited resources toward
the conservation of biodiversity. 相似文献
73.
Jerome Taveau 《Journal of Loss Prevention in the Process Industries》2010,23(1):15-29
Empirical correlations are often used to estimate safety distances in the event of dust explosions. In Europe, there are two main correlations available in VDI 3673 and EN 14491. Whereas the VDI 3673 correlation is based on experimental investigations of vented dust explosions using large vessels, and assumes an external explosion, the EN 14491 correlation is derived from SKJELTORP et al. internal explosion tests in ammunition storage facility. This paper provides an overview of the experimental studies of vented gas and dust explosion. It aims to highlight the main findings of such studies, while defining the conditions for a secondary explosion to occur and comparing experimental data with the application of standards, in order to propose elements to choose the more appropriate correlation. 相似文献
74.
Jerome R. Ravetz 《Journal of Agricultural and Environmental Ethics》2002,15(3):255-265
I argue that the issues of foodquality, in the most general sense includingpurity, safety, and ethics, can no longer beresolved through ``normal' science andregulation. The reliance on reductionistscience as the basis for policy andimplementation has shown itself to beinadequate. I use several borderline examplesbetween drugs and foods, particularly coffeeand sucrose, to show that ``quality' is now acomplex attribute. For in those cases thesubstance is either a pure drug, or a bad foodwith drug-like properties; both are marketed asif they were foods. An example of theinadequacy of old ways of thinking is obesity,whose causes are as yet outside the purview ofmedicine, while its effects constitute anepidemic disease. The new drug/food syndromeneeds a new sort of science, what we call``post-normal.' This is inquiry at the contestedinterfaces of science and policy; typically itdeals with issues where facts are uncertain,values in dispute, stakes high, and decisionsurgent. With the perspective of post-normalscience, we can better understand some keyissues. We see that ``safety' is different from``risk,' being pragmatic, moral, and recursive.Also, we understand that an appropriatefoundation for regulation and ethics is not somuch ``objectivity' as ``awareness.' In an agewhen ``consumers' are becoming concerned``citizens,' the relevant science must becomepost-normal. 相似文献
75.
76.
77.
Effects of species diversity on community biomass production change over the course of succession 总被引:5,自引:0,他引:5
Over the past decade an increasing number of studies have experimentally manipulated the number of species in a community and examined how this alters the aggregate production of species biomass. Many of these studies have shown that the effects of richness on biomass change through time, but we have limited understanding of the mechanisms that produce these dynamic trends. Here we report the results of an experiment in which we manipulated the richness of freshwater algae in laboratory microcosms. We used two experimental designs (additive and substitutive) that make different assumptions about how patches are initially colonized, and then tracked the development of community biomass from the point of initial colonization through a period of 6-12 generations of the focal species. We found that the effect of initial species richness on biomass production qualitatively shifted twice over the course of the experiment. The first shift occurred as species transitioned from density-independent to dependent phases of population growth. At this time, intraspecific competition caused monocultures to approach their respective carrying capacities more slowly than polycultures. As a consequence, species tended to over-yield for a brief time, generating a positive, but transient effect of diversity on community biomass. The second shift occurred as communities approached carrying capacity. At this time, strong interspecific interactions caused biomass to be dominated by the competitively superior species in polycultures. As this species had the lowest carrying capacity, a negative effect of diversity on biomass resulted in late succession. Although these two shifts produced dynamics that appeared complex, we show that the patterns can be fit to a simple Lotka-Volterra model of competition. Our results suggest that the effects of algal diversity on primary production change in a predictable sequence through successional time. 相似文献
78.
This article focuses on developing a sustainable tourism in small Caribbean islands, defined here as those that have populations
of fewer than 500,000. Such islands share a very fragile ecology and a high dependence on tourism. They differ in their degree
of tourist penetration and visitor density and the related degree of environmental degradation.
To explain the link between tourism intensity and ecological vulnerability, the so-called “destination life-cycle model” is
presented. This suggests that islands pass through three primary stages of tourist development low-density exploration, rapid
growth and consolidation, and high-density maturation involving the substitution of man-made for natural attractions.
A broad empirical test of the model is performed through a quantitative examination of the tourism characteristics and visitor
densities of a cross section of 23 small Caribbean islands. The three basic stages or tourism styles are identified: low-impact
emerging areas, high-density mass-market mature destinations, and rapidly growing intermediate islands in between. Some broad
strategies consistent with the systems framework for a sustainable tourism with moderate densitites are briefly explored.
An earlier version of this article was presented to Caribbean Conservation Association Conference on Economics and the Environment.
Barbados, West Indies, 6–8 November, 1989. 相似文献
79.
Siegel J 《Die Naturwissenschaften》2004,91(8):355-365
This review paper presents a brief historical survey of the technological and early research that laid the groundwork for recent advances in sleep–waking research. A major advance in this field occurred shortly after the end of World War II with the discovery of the ascending reticular activating system (ARAS) as the neural source in the brain stem of the waking state. Subsequent research showed that the brain stem activating system produced cortical arousal via two pathways: a dorsal route through the thalamus and a ventral route through the hypothalamus and basal forebrain. The nuclei, pathways, and neurotransmitters that comprise the multiple components of these arousal systems are described. Sleep is now recognized as being composed of two very different states: rapid eye movements (REMs) sleep and non-REM sleep. The major findings on the neural mechanisms that control these two sleep states are presented. This review ends with a discussion of two current views on the function of sleep: to maintain the integrity of the immune system and to enhance memory consolidation.This article is based in part on material in the book The neural control of sleep and waking (J. Siegel, 2002). 相似文献
80.
Jerome Buhl Gregory A. Sword Fiona J. Clissold Stephen J. Simpson 《Behavioral ecology and sociobiology》2011,65(2):265-273
Locust swarms are spectacular and damaging manifestations of animal collective movement. Here, we capture fundamental features
of locust mass movement in the field, including a strongly non-linear relationship between collective alignment and density
known only from earlier theoretical models and laboratory experiments. Migratory bands had a distinct structure, with a single
high-density peak at the front, where collective alignment was high, followed by an exponential decay in density. As predicted
by theory, alignment decreased with decreasing density, and fluctuations of movement direction became large until order amongst
group members at the back of the band was totally lost. Remarkably, we found that the coordinated movement of migratory bands,
which can be several kilometres wide and contain many millions of individuals, results from interactions occurring at a scale
of 13.5 cm or less. Our results indicate that locust band structure and dynamics differ markedly from what is known (or assumed)
about other large moving groups such as fish schools or bird flocks, yet they still conform to key general predictions made
by collective movement models that explain how billions of individuals can align using local interactions. 相似文献